1. Field of the Invention
The present invention relates to a method for manufacturing a hardcoat film and a hardcoat film.
2. Description of the Related Art
In recent years, for hardcoat films obtained by providing a hardcoat layer on a base material, there has been a strong demand for providing multiple functions by laminating other layers, for example, an antistatic layer, a high-refractive index layer, a layer of low refractive index, a phase difference layer, a bonding layer, and the like depending on applications. In the case of being produced by curing a compound having an ethylenic unsaturated double-bonding group, hardcoat layers have hydrophobic surfaces in many cases. In a case in which other layers are laminated on a hardcoat layer, when the surface of the hardcoat layer serving as an underlayer is hydrophobic, a hydrophilic composition being used as a coating composition for the upper layer does not gradually wet the hardcoat layer and remains in a separated state. Therefore, when the surface of the hardcoat layer is made to be hydrophilic (to have a small contact angle of water), it is possible to form a homogeneous coated film having no cissing on the upper layer.
For example, JP2001-272503A describes that a hardcoat layer is provided by means of coating, and then a corona discharge treatment or a glow discharge treatment is carried out, thereby decreasing the contact angle with respect to water.
In addition, JP2002-265866A describes that a surface treatment such as an alkali treatment or a corona treatment is carried out on the hardcoat layer, thereby improving adhesiveness to a layer of low refractive index as the upper layer.
Meanwhile, in order to make the coated film of the hardcoat layer smooth, a method in which a surfactant (a leveling agent) such as a silicone-based compound or a fluorine group-containing polymer is added to a composition for forming the hardcoat layer is generally used. It is considered that the surfactant is locally present on the surface of the coated film due to its hydrophobicity and decreases the surface tension of the coated film, thereby imparting levelability. However, the above-described surfactant remains on the surface of the hardcoat layer even after the curing of the film and thus hydrophobilizes the surface, which creates a problem in laminating other layers on the hardcoat layer as described above.
As a method for hydrophilizing the surface of the hardcoat layer while maintaining the levelability, JP2001-272503A describes that the addition of an anionic, nonionic, or betainic surfactant decreases the contact angle of water.
In addition, JP2011-212554A describes that a specific amount of a solvent having a boiling point and a viscosity in a specific range is used without using any surfactants.